1. Field of the Invention
The field of art to which this invention pertains is high voltage generating circuits for color television receivers and in particular to circuits for producing good high voltage regulation under conditions of low load and high current load.
2. Description of the Prior Art
Prior art high voltage generating circuits for television receivers, have hitherto used so-called pulse rectifying systems in which the resonant frequency in a flyback transformer is selected to be higher than the horizontal sweep frequency of 15.75 KHz, that is, for example, about 50 KHz. This flyback transformer generated a high voltage pulse of the horizontal sweep period having a narrow pulse width, and this high voltage pulse was then peak-value-rectified by a diode rectifier circuit. Such a prior art pulse rectifying system has the drawback that when the high voltage load current increases, the high voltage is undesirably lowered since the angle of current flow of the diode in the rectifier circuit is quite small and hence the regulation is inferior.
Further, there has been considered a system wherein the high voltage pulse is converted into a sinusoidal voltage by using a resonant circuit which is tuned in the vicinity of the horizontal sweep frequency, and this sinusoidal voltage is rectified by a diode rectifier circuit to obtain the desired high voltage. According to the so-called sinusoidal rectifying system, to rectify the sinusoidal voltage, the angle of current flow of the diode in the rectifier circuit becomes wider than that of the pulse rectifying system, and the regulation of the high voltage is slightly improved. However, even in the sinusoidal rectifying system, there is the problem that when the high voltage load current is changed the resonant frequency of the resonant circuit will also be changed and hence the high voltage will be varied undesirably.